4. (30 Points) Assume a string str and each character is stored as one byte. Convert the following high-level code into RISC-V assembly language. Assume that the array base address is stored in register ao, the index variable i is stored in register to and the count variable count is stored in the register t1. a) if (str[i] < '0' or str[i] > '9') count = count + 1; b) if (str[i] >= 'a' and str[i]