Theory:

Bela Raja: Was it then that you decided you wanted to do architecture?

Hafeez Contractor: Actually, it all happened quite by chance.
 
     In the architect’s office, I saw somebody drawing a window detail. A window detail is a very advanced drawing.

     I told him that his drawing was wrong — that the window he had drawn would not open.

     He then had a bet with me and later he found that indeed, his drawing was wrong! My cousin’s husband was surprised. He asked me to draw a few specific things, which I immediately did.

     He asked me to design a house and I designed a house. After that, he told me to drop everything and join architecture.
Explanation:
 
Ms Bela asked Hafeez, "Was it then that you decided you wanted to do architecture?" Hafeez said that nothing had been planned previously. According to him, getting into the field of architecture happened by chance. Then, he started to narrate an incident that occurred earlier. The incident had made him to become an architect.

On a fine day in the architect’s office, Hafeez saw an advanced drawing of a window detail designed by an office employee. Hafeez examined the design and informed him that there was an error in the sketch since the window he had sketched might not open. Then the man had a bet with Hafeez thinking that his drawing was correct.

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Hafeez saw a man drawing a window detail
 
However, the man's sketch was incorrect, and Hafeez's remark was correct. When his cousin's husband saw this, he was taken aback by his expertise and requested him to sketch a few things for him. He did so right away. The architect told him to design a house, and he did it perfectly. Hafeez's ability surprised the architect, who recommended him to begin studying architecture. His cousin's husband recognised Hafeez's abilities and encouraged him to drop out of other activities and pursue higher education. This is how he decided to undertake architecture.
 
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Hafeez has drawn a house design
 
Meanings of the difficult words:
 
S.No
Words
Meanings
1
Surprise
An unexpected or astonishing event, fact, or thing
2
Design A plan or drawing produced to show the look and function or workings of a building, garment, or other object before it is built or made
3
EmployeeA person employed for wages or salary, especially at non-executive level
4
Expertise Expert skill or knowledge in a particular field
Reference:
National Council of Educational Research and Training (2008). It so happened. The Treasure Within (pp. 25-33). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.