Determine f(x) given that f'(x)= cos(x)-sin(x) and f(π/2)=7

In january 2014 and i started 1 million pennies project she put donation jars in school and shops and set up a webpage to of said donations online her gold was to collect 1 million pennies or 1000 chandra’s planned to give the money to a group called growing food for the group plant gardens and deliver the products it grows to people in need