.
I will solve and answer part (a) only.
ANSWER. There are two and only two possible collections :
- one is { 2 pennies, 3 quarters and 3 dimes }
- and the other is { 2 pennies, 1 quarter and 8 dimes }.
Explanation.
1) The only alternative to 2 pennies is to have 7 pennies, or 12 pennies, or 17 pennies (and so on . . . ) to make a total of $1.07.
But these alternatives contradict to be not able to make a change for a dollar.
So, 2 pennies is the only option, regarding pennies.
2) OK. It leaves us with $1.05.
Then we must be able to make $1.05 using quarters and dimes only, without being able to make change for a dollar.
Again, it is obvious that there are only two such opportunities :
- one quarter and 8 dimes,
and/or
- three quarters and 3 dimes.