Billy runs a corner shop. He is having a New Year sale and decides to reduce the price of cornflakes by dropping the profit he makes on each packet (i. e. his selling price minus his buying price) by 25%. He finds that, during the week of his sale, he has made 20% more profit on cornflakes than he usually does. By what percentage did the number of packets of cornflakes sold increase during the sales week compared with a normal week?

A: 20%
B: 45%
C: 60%
D: 80%

Ps: I would greatly appreciate if you took a shot at this problem and help me out. I’m in the Cambridge academy and my Critical Thinking class is really hard. The answer would help me but I’m looking at the process so I can understand it. Thank you guys for your help! Really