Answer:
[tex]B=40[/tex]
Step-by-step explanation:
we know that
[tex](a+b)^{2}=a^{2}+2ab+b^{2}[/tex]
In this problem we have
[tex](4a+5)^{2}=16a^{2}+Ba+25[/tex]
The second term of the trinomial is equal to
[tex]2(4a)(5)=40a[/tex]
therefore
[tex]B=40[/tex]
