Solve #$1$ and #$2$

$1.$ A fan is used to produce a constant air velocity of $4000$ fpm throughout the $40-$inch round duct loop shown below. Each of the four $90$ degree elbows has an equivalent length of $60$ feet. Determine the volumetric flow rate $($cfm$)$ and head pressure loss $($in inches of water column$)$ that the fan must overcome. Use the Darcy$-$Colebrook chart. $(3$ points$)$

$2.$ Repeat Problem #$1$ for a rectangular duct measuring $52$ x$24$ inches. Use the same equivalent lengths and same air velocity. $(3$ points$)$