Why would Governments use Price Caps, and what are the 2 Types?

-Price Caps are a form of Regulation, and they put a Maximum or Minimum -RPI-X: Firms make Real Price Cuts. RPI is Inflation and X is Efficiency Improvements the Government Expects. (THE - IS A MINUS) -RPI-X+K: Seen in the Water Industry, K is the Amount of Investment Firms need to make to Achieve Efficiency Improvements. Therefore, the Firm can make Higher Prices