please answer these questions

4. A company invested $2,500,000 in a tool that has a service life of 10 years and salvage value of $250,000. If it costs $50,000 per year to maintain, what is its annual cost, given that the current interest rate is 8% and is expected to remain constant? (16 marks) 5. A firm is considering engineering projects A,B and C, with cash flows (in thousands) estimated in the table below. Determine which machine is most economical by either discounting all costs to the present or using the annual cost, given the current interest is 12% and is expected to remain constant. (25 marks) 6. A sector of a circle encloses an area of 25cm2. Find the least possible perimeter of the sector (16 marks) 7. Given the objective function Z=10x+15y, subject to: 2x+5y504x+2y36x,y0 Find the value of x and y that maximizes Z, and state the maximum value of Z (16 marks)