With #4 physics i really need guys!

5A

Method 1

For R₂, V=IR,

V₂ = 2.5×8

  = 20 V

Since the voltage across each branch of the parallel circuit is the same, the voltage across R₂ is equal to that of R₃.

So, for R₃, V₃=20V

V=IR

20 = I × 4

I = 5A

Method 2

In parallel circuit, the ratio of the resistance in each branch are inversely proportional to the ratio of current in each branch.

no. dot product   =0 when vecs at right angles