A pair contains two numbers in an array with its second number is on the right side (not necessary immediately right) of the first one in an array. The difference of a pair is the minus result while subtracting the second number from the first one. Please :

a. Use the divide and conquer methodology to design an efficient algorithm to find the maximal difference of all pairs in an array. For example, the maximal difference in the array {2, 4, 1, 16, 7, 5, 11, 3} is 13, which is the minus result of pair (16, 3).

b. Analyze the computing complexity of your algorithm.