In survey people were asked if they took avacation in the summer, winter or spring in the past year. the result were 78 were took avaccation in the summer 55 took avaccation in winter 31 took vacation in spring and 2 had took no vaccation also 15 had take vacation at all 3 times, 35 had take both summer and winter and vaccation 18 had take only winter vacation, 47 had both a summer and spring but not winter vaccation a, how many people had been survived? b, how many take exactly two times
c, how many people at most one time ?​