Three activities are candidates for crashing on a project network for a large computer installation $($all are, of course,

critical$).$ Activity details are in the following table:

a$)$ Activity that should be crashed first to reduce the project duration by $1$ day is

b$)$ Activity that should be crashed next to reduce the project duration by one additional day is $B$

c$)$ Total cost of crashing the project by $2$ days $=$$$,.($Enter your response as an integer.$)$