Caleb earns $10 per hour. He worked 4 hours on Monday, Wednesday, and Friday. He worked 8 hours on Tuesday and Thursday. Which expression can be simplified to determine that total amount Caleb earned.
a. (3x4+2x8)x10 c. (3x4)+2x8x10
b. 3x4+2x8x10 d. 3x4+(2x8x10)