Consider the following linear program, where A and $B$ are the two decision variables:

Max $1A+2B$

S$.$t$.A5$

$(1)$

B

$(2)$

$2A+2B12$

$A,B0$

How much is the dual value of Constraint $(1)?$

A$.1$

B$.5$

c$.$

D$.$ Cannot be determined.