Consider the Scala program:

def f$()$: Int $=>$ Unit $=\{$

var x: Int $=0$

def g$($y: Int$)$: Unit $=\{$ x $+=$ y; print$($x $+",")\}$

g

$\}$

val h$1=$ f$()$

h$1(3)$; h$1(4)$

val h$2=$ f$()$

h$2(3)$; h$2(4)$

h$1(3)$; h$1(4)$

What will happen when the program is executed?

Program self destructs in a puff of smoke.

Prints: $3,4,3,4,$

Prints: $3,7,3,7,$

Prints: $3,7,10,14,17,21,$

Prints: $3,7,3,7,10,14,$