In a class of 50 pupils, it was found that 4 take maths and Bio only,3 take maths and Chem only and 6 take Bio and Chem only. Furthermore, 7 take maths alone, 5 take Bio alone and 8 take chem alone. If 2 take non of the above subjects, find : a) the number of pupils doing all the 3 subjects (3mks) ; b)the number of pupils taking maths and chem.(3mks)​