Solve for Variables: Hard

The answer is c+(N-1)(c-d).
There are N candy bars.
The first one cost c dollars, the remaining N-1 candy bars cost (c-d) dollars each.
Therefore, the N-1 remaining candy bars cost (N-1)(c-d) dollars.
The total cost is equal to the cost of the first candy bar, plus the cost of the N-1 remaining candy bars.
Total cost=c+(N-1)(c+d).