IKMC 2021 - Grades 5-6 - Self-study Question 12

The map shows stations A, B, C. Tours A–Zoo–Port–A, B–Park–Zoo–B, C–Port–Park–C have lengths 10, 12, 13 km. The Zoo–Park–Port–Zoo tour is 15 km. How long is the shortest A–B–C–A tour?