1. [15\%] A computer system has 1Gbytes of DRAM and runs 10 processes. The virtual address has 32 bits, page size is 4Kbytes, and each page table entry (PTE) occupies 4 bytes. Assume that each process has its code and data together stored in the lowest 6Mbytes and stack stored in the highest 12Kbytes of its virtual address space. If the following page table implementations are used, what is total memory size of page table(s) the OS must allocate for these processes? (a) [5\%] 1-level page tables (b) [5\%] 2-level page tables (In addition to the page offset field, a virtual address has a 10-bit first-level page table field and a 10-bit second-level page table field) (c) [5\%] Inverted page table (assuming that the PTE size of the inverted page table is also 4 bytes)