write a purely recursive function that takes a string c, and a string st, and which returns a list of strings consisting exactly of all the strings that can be formed by placing c in every possible position in st. you may not use any looping control structures such as for or while loops. you must use only the most basic and primitive python commands

for example, if c = 'x' and st = 'hello', then the output should look like ['xhello','hxello','hexllo','helxlo','hellxo','hellox']