Question $1(5$ points$)$

What is the equivalent length of a butterfly valve in $4$ in$.$ Sch $10$ pipe being used in an automatic wet standpipe system?

a$)17\mathrm{.}3$

b$)21\mathrm{.}8$

c$)12\mathrm{.}6$

d$)15\mathrm{.}8$