Answer: $1690
Step-by-step explanation: because there are 3 people which means the flat fee would add up to 90 (because 30x3=90). Then you have to multiply 400 by 4 to get how much money they spent for renting the boat (400x4=1600). Lastly you add 1600 and 90 to get the final price. (1600+90=1690).