Define an algorithm G$\text{'}$ where G$\text{'}($s$)=$ G$($s$1$ sn$2),$ where s $=$ s$1$ sn and si represents the i$-$th bit of s$,$ where G is a pseudorandom generator with expansion factor l$($n$)>2$n$.$

Consider a modified version of the $$pseudo$-$one$-$time pad $($Construction $3\mathrm{.}17)$ based on a pseudorandom generator G$.$ The key generation algorithm stays the same as before. The encryption algorithm $($in this modified version of the scheme$)$ on input a key k and a message m$,$ encrypts the message as G$\text{'}($k$)$ m$.$

$($a$)$ How can decryption be done?

$($b$)$ What is the message space over which this encryption scheme is defined?

$($c$)$ Does this scheme have indistinguishable encryptions in the presence of an eavesdropper? Prove or disprove your answer.

$($d$)$ Is this scheme CPA$-$secure$?$ Explain your answer.