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.