The amount of $$ROM$$ needed to implement a $$4$$ bit multiplier is

A main memory unit with a capacity of $$4$$ megabytes is built using $$1M \times 1$$-bit $$DRAM$$ chips. Each $$DRAM$$ chip has $$1K$$ rows of cells with $$1K$$ cells in each row. The time taken for a single refresh operation is $$100$$ nanoseconds. The time required to perform one refresh operation on all the cells in the memory unit is

How many $$32k$$ x $$1$$ $$RAM$$ chips are needed to provide a memory capacity of $$256$$ $$K$$-bytes?

Consider a $$4$$-way set associative cache consisting of $$128$$ lines with a line size of $$64$$ words. The $$CPU$$ generates a $$20$$-bit address of a word in main memory. The numbers of bits in the TAG, LINE and WORD fields are respectively