The monthly principal plus interest 12000 yuan, excluding the principal 10000 yuan, the interest is 2000 yuan, and the monthly interest 10 yuan totals 20000 yuan, accounting for 20% of the principal.

After the first 10 month, the interest with principal = 100000X( 1+20%).

After the second month 10, the interest with principal =100000x (1+20%) x (1+20%).

Five years adds up to 60 months

10 After the sixth month, the principal =100000x (1+20%) 6 = interest of 298598.4 yuan.

absolutely true