Write a C program named as listLetterFreq. c that lists the frequency of the letters from the input via ignoring the case sensitivity. For example, sample outputs could be like below $cat test. txt This is a list of courses. CSC 1010 - COMPUTERS & APPLICATIONS $./ listLetterFreq < test. txt Letter a or A appears 3 times Letter b or B appears 0 times Letter c or C appears 5 times Letter d or D appears 0 times Letter e or E appears 2 times Letter f or F appears 1 times Letter g or G appears 0 times Letter h or H appears 1 times Letter i or I appears 5 times Letter j or J appears 0 times Letter k or K appears 0 times Letter l or L appears 2 times Letter m or M appears 1 times Letter n or N appears 1 times Letter o or O appears 4 times Letter p or P appears 3 times Letter q or Q appears 0 times Letter r or R appears 2 times Letter s or S appears 8 times Letter t or T appears 4 times Letter u or U appears 2 times Letter v or V appears 0 times Letter w or W appears 0 times Letter x or X appears 0 times Letter y or Y appears 0 times Letter z or Z appears 0 times