(a) A rectangular area of 2000 ft; is to be fenced off. Two opposite sides will use fencing costing 40 taka per foot and the remaining sides will use fencing costing 50 ta ka per foot. Find the dimensions of the rectangle of least cost and compute the least cost. 4. (31} Find the area of the region below y = x In 3: over the interval [1, e]. dx \"'1 f lam