Write a function combined_cases(day1_cases, day2_cases) which take in two input parameters which are two dictionaries that represent the COVID-19 cases on one specific day in different states in the USA. Your function should return a dictionary that contains the sum of the cases of the two days in the given states.

For example:

If the following two dictionaries are given as input:

day1_cases = {'Texas': 10678, 'Florida': 7459, 'Illinois': 12601}
day2_cases = {'Texas': 13379, 'Florida': 7925, 'Illinois': 11301}

Then your function must return:

{'Texas': 24057, 'Florida': 15384, 'Illinois': 23902}

Sample Input:

{'California': 10577, 'New York': 5167}
{'California': 11835, 'New York': 5364}

Sample Output:

{'California': 22412, 'New York': 10531}