If the White Rock Fire Department invests now in new ladder systems for several of their trucks, they would save $3500 every six months in repair costs. What single cash investment made now is equivalent to the repair payments if interest is 8% compounded quarterly and the payments are made

(a) at the end of every six months for fifteen years?

(b) at the beginning of every six months for ten years?

(c) at the end of every six months for eight years but deferred for four years?

(d) at the beginning for every six months for nine years but deferred for three years?

(e) at the end of every six months in perpetuity?

(f) at the beginning of every six months in perpetuity?