The value of a car can be modelled by the function, V = 300/18 sin(t/16)+7cos (t/16), where, Vis the value of the car in thousands t is the time in years since the car was purchased. a Express 18sin+7 cos.e in the form R(sin + a), where R> 0 and 0 < a < 5- Give the exact value of R and the value of a, in radians, to 2 decimal places. b Find the time, in years, that it will take for the car to be worth half of its original purchase price. c Find the time taken for the value of the car to reach its minimum value. d Explain with a reason why this model is not valid for large values of t. (4) (2) (1)