6. It is estimated that the total cost of constructing a condominium floors high is C(x)=x2+250x+600(RM000). If x=10, find a) The total cost, b) The average cost per floor. (2 marks) c) The marginal cost of producing the 10th floor. (2 marks) (4 marks) 7. Jaslin bought an electric piano through an instalment plan in which she had to pay RM 1000 down. The balance was settled by making 36 monthly payments of RM100 each. If the dealer charged her an interest of 9% per annum on the original balance, find the cash price of the item. (6 marks)