Categorize the following contracts as valid, invalid, or imperfect.

a. An Islamic bank provides financing to build a Masjid.

b. Rajoo Islamic bank provides interest to its depositors.

c. Ali signs up for a family takaful policy (similar to life insurance).

d. An Islamic bank in country X enters into an istisna contract to finance the building of a prostitution center. Prostitution is legal in the country.

e. An Islamic bank provides murabaha financing for a car already owned by Ahmad.

f. An underaged boy enters into a loan agreement with his friend.

g. Kathija is forced to sell her car for $10,000 (less than the market value) to Kevin by Nathan, who is a paraplegic using a wheelchair.