Hi, can someone please explained the answer for part a and b in details please and thanks :D

3. Let X denote the amount (in litres) of petrol stocked by a service station at the beginning of a week and suppose that X has a uniform distribution over the interval [10000, 20000]. Suppose the amount Y of petrol sold during a week has a uniform distribution over the interval [10000, X] (a) Find the joint density function of X and Y. (b) If the service station lls up to 15,000 litres at the beginning of a week, What is the probability that the amount of petrol sold in that week is greater than 12, 000 litres? (o) If it is known that the service station sold 12, 500 litres, what is the probability that the amount stocked was greater than 15, 000 litres? Solution: (a) For an E (10000, 20000] and y E [10000,25], bra/(13,140 : leX(yl$)fX($) 1 10000(;c 10000) ' 15000 1 MY 2 12000|X = 15000) f dy 12000 5000 II to \\u. 3-&quot