Consider the triangles ABC and KBM.
∠B is common.
∠BAC = ∠BKM (since these are the corresponding angles)
∠BCA = ∠BMK (since these are also the corresponding angles)
Therefore, these triangles are similar in the first sign of similarity.
Then by the definition of such triangles:
BA / BK = AC / KM
(BK + KA) / BK = AC / KM
1 + KA / BK = AC / KM
1 + 4/1 = AC / KM
5 = AC / 13
AC = 5 * 13 = 65
Answer: AC = 65
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.