KöMaL 2018 K589

A company regularly hires the same man to mow a certain grassy area. In addition to the labour cost, the man charges a call-out fee of 5000 forints (HUF, Hungarian currency). If he mows the grass three times a month, the labour cost is 1.8 times as much per occasion as it is in the case when he mows the grass four times a month, since in the former case the grass will grow higher which requires more work. On the whole, it is more economical for the company to have the grass mowed four times a month. What is the minimum possible labour cost per mowing in the case of 4 occasions a month, given that it is an integer multiple of 100 forints?