If cos(A)=1/7\cos(A) = 1/7cos(A)=1/7 and cos(B)=13/14\cos(B) = 13/14cos(B)=13/14 where A,BA, BA,B are in the first quadrant, what is the value of A−BA-BA−B?
30∘30^\circ30∘
45∘45^\circ45∘
60∘60^\circ60∘
90∘90^\circ90∘