4) First, maximize the quarters, then maximize the dimes with what's left, then repeat for the nickels and pennies.
So, use 3 quarters for 75 cents
Then, use 1 dime to get to 85
Then, use 1 nickel to get to 90
Then, use 3 pennies to get to 93
So \(3 + 3 + 1 + 1 = \color{brown}\boxed{8}\) coins.