Let c be a positive real number. Let X and Y be two continous random variables with the joint pdf f

$($

x

$,$

y

$)$

$=$

$$c if

$0$

$<$

$=$

x

$,$

y

$<$

$=$

$1$

$$and x

$+$

y

$<$

$=$

$1$

$,$

$$ or

$-$

$1$

$<$

$=$

x

$<$

$=$

$0$

$,$

$0$

$<$

$=$

y

$<$

$=$

$1$

$$and

$-$

x

$+$

y

$<$

$=$

$1.$

$$Derive the constant c

$,$

using the defininig properties of a cdf$.$ Is c $2?$ Why or why not?