Situation A: A $20-$kg block is pressed against a relaxed spring on a frictionless surface. The

spring is compressed by $$x $=10$ cm from its equilibrium position x $=$ x$$

e$.$ The block is released

and the spring uncompresses. The speed of the block at x $=$ x$$

e is va$,$f $=5\mathrm{.}0$ m$/$s$.$

$$ Situation B: The same $20-$kg block is pressed against two relaxed springs that are attached in

series on a frictionless surface. $($These two springs are both identical to the spring in Situation A$).$

The entire spring assembly is compressed by $$x $=10$ cm from its equilibrium position x $=$ x$$

e$.$

The block is released and the spring assembly uncompresses. The speed of the block at x $=$ x$$

e is

vb$,$f $.$

Question: What is the value of vb$,$f $?$

$($A$)3\mathrm{.}5$ m$/$s

$($B$)2\mathrm{.}5$ m$/$s$/$s

$($C$)5\mathrm{.}0$ m$/$s

$($D$)6\mathrm{.}4$ m$/$s

$($E$)7\mathrm{.}0$ m$/$