Can you help me with the highlighted portion please? Let X = {n EN: 0≤ n ≤ 999} be the set of all numbers with three or fewer digits.Define the function ƒ : X → N by f(abc) = a +b+c, where a, b, and c are the digitsof the number in X (write numbers less than 100 with leading O's to make them threedigits). In other words, f returns the sum of the digits of its input. For example,f(253) = 2+5+ 3 = 10.a. Let A = {n € X : 308 ≤ x ≤ 325}. Find f(A).{4,5,6,7,8,9,10,11,12b. Find f-¹({1,3}){1,10,100,120,102,12c. Find f-¹(2).{2,11,20,101,110,20Cd. Find f ¹(287).

Here,there does not exist any number in X such that the sum of the digits is equal to 287.i.e. we…

Let X = {n € N : 0≤ n ≤ 999} be the set of all numbers with three or fewer digits. Define the function ƒ : X → N by f(abc) = a +b+c, where a, b, and c are the digits of the number in X (write numbers less than 100 with leading 0's to make them three digits). In other words, f returns the sum of the digits of its input. For example, f(253) = 2+5+3 = 10. a. Let A = {n € X : 308 ≤ x ≤ 325}. Find f(A). {4,5,6,7,8,9,10,11,12 b. Find f-¹({1,3}) {1,10,100,120,102,12 c. Find f-¹(2). {2,11,20,101,110,20C d. Find f-¹(287).