The total monthly bill for 30 Mbps is $20 x 2= $<<20*2=40>>40.
She will have to pay $40 x 12 = $<<40*12=480>>480 every year for 30mbps.
The total monthly bill for 20 Mbps is $20 + $10= $<<20+10=30>>30.
So, she will have to pay $30 x 12 = $<<30*12=360>>360 for 20 Mbps per year.
Therefore the amount she will save per year if she chooses the 20mbps is $480 - $360 = $<<480-360=120>>120
#### 120