Consider the integral ${\displaystyle \underset{0}{\overset{4}{}}}{\displaystyle \underset{0}{\overset{\sqrt[\phantom{2}]{16-y}}{}}}f(x,y)dxdy.Ifwe$ change the order $of$ integration $we$ obtain the sum $of$ two integrals:

${\displaystyle \underset{a}{\overset{b}{}}}{\displaystyle \underset{g_1(x)}{\overset{g_2(x)}{}}}f(x,y)dydx+{\displaystyle \underset{c}{\overset{d}{}}}{\displaystyle \underset{g_3(x)}{\overset{g_4(x)}{}}}f(x,y)dydx$

$a=b=$

$g_1(x)=$

$c=b{g}_2(x)=$

$g_3(x)=,g_4(x)=$