Assume you can only use 7-cent and 11-cent stamps.
a) Determine which amounts of postage can be formed by the given stamps.
b) Prove your answer using the principle of mathematical induction.
c) Prove your answer using strong induction.
By doing a) i found out that all the numbers after 59 can be created using a combination of 7 cants and 11 cents stamps
In part b , i assumed that the $$ n=7k+11l$$ where k is the amount of 7 cents stamps and l is the amount of 11 cents stamps. But how do i proceed? And in the strong induction step what is our inductive hypothesis?