Answer:
(q2 - q1)
Step-by-step explanation:
I have uploaded the picture the question refers to below.
We can see that under a price ceiling of $0, the quantity of kidneys supplied is Q1, and if the price ceiling is removed, and the market is allowed to reach equilibrium, the new quantity of kidneys supplied is Q2, so the increase in the supply of transplanted kidneys can be found by the formula (q2 - q1)