Without time information, only with input of two meter readings and the price per kW/h, only the total price between the two meter readings can be calculated. Under the current consumption I would understand something else.
As CPallini has already mentioned, these are only numerical values. If still the date or text inputs should become necessary, the effort would be higher. The background is that one should secure programs in principle against incorrect user inputs. There are countless possibilities, what can go wrong and some things could lead to a crash of the program or to wrong results. The approach to read everything as text first, as Rick York suggests, to be able to check it then and also to be able to print a meaningful error message is a bit more complex but works for most of the input you want to get from a user. To turn a string into a number you could use strtol(). So it would be possible to read all numbers in one line. This is especially good if the numbers are in a text file.
Here is an example for strtol()
https://www.tutorialspoint.com/c_standard_library/c_function_strtol.htm
For other input formats there is a lot more, but that would lead too far here.