Vertices of a variable acute-angled triangle ABC lie on a circle of radius R such that da/dA + db/dB + dc/dC = 6. Distance of orthocentre of triangle ABC from vertices A, B and C is x_{1}, x_{2} and x_{3}, respectively

**1. In-radius of triangle ABC is **

(A) 1

(B) 2

(C) 3

(D) 4

**2. Maximum value of x**_{1}x_{2}x_{3} is

(A) 4

(B) 6

(C) 8

(D) 10

**3. dx**_{1}/da + dx_{2}/db + dx_{3}/dc_{ } is always less than equal to

(A) -3√3

(B) 3√3

(c) 1

(D) 6