Does someone know how to solve this problem?

Acute scalene triangle.

Step-by-step explanation:

Acute scalene triangle.

Sides: a = 4   b = 7   c = 8

Area: T = 13.998

Perimeter: p = 19

Semiperimeter: s = 9.5

Angle ∠ A = α = 29.995° = 29°59'41″ = 0.524 rad

Angle ∠ B = β = 61.028° = 61°1'42″ = 1.065 rad

Angle ∠ C = γ = 88.977° = 88°58'37″ = 1.553 rad

Height: ha = 6.999

Height: hb = 3.999

Height: hc = 3.499

Median: ma = 7.246

Median: mb = 5.268

Median: mc = 4.062

Inradius: r = 1.473

Circumradius: R = 4.001

Vertex coordinates: A[8; 0] B[0; 0] C[1.938; 3.499]

Centroid: CG[3.313; 1.166]

Coordinates of the circumscribed circle: U[4; 0.071]

Coordinates of the inscribed circle: I[2.5; 1.473]

Exterior (or external, outer) angles of the triangle:

∠ A' = α' = 150.005° = 150°19″ = 0.524 rad

∠ B' = β' = 118.972° = 118°58'18″ = 1.065 rad

∠ C' = γ' = 91.023° = 91°1'23″ = 1.553 rad

the answer is b