Problem Solving

In a group of 100 students, 60 have completed MBA. Anyone who has completed MBA has done an undergraduation in one of the three streams - Engineering, B.com or BBA. No engineer has done both B.com and BBA and there are 12 students who have done both B.com and BBA. There are 50 engineers of whom 30 have also completed an MBA. 30 students have completed B.com. There are exactly 34 students who have done exactly one degree. The number of students who have done B.com and MBA is the same as those who have done BBA and MBA. How many have done a BBA?

a) 32
b)28
c)30
d)26
e)27

OA is A
Can an expert give the logical breakdown for this question? Thanks