Bookwork code: CO2 Calculator The diagram below shows the totals from adding together the results from spinning two fair four-sided spinners. a) What number should replace $A$ ? b) What is the probability of the total being 4 ? Give your answer as a fraction.

Step 1 ：Find the sum of the numbers in the last row and last column: \(1+2+3+4=10\) for both.

Step 2 ：Replace A with the sum of the last row and last column: \(A=10+10=20\)

Step 3 ：Count the number of ways to get a sum of 4: There are 3 ways.

Step 4 ：Calculate the probability of the total being 4: \(\frac{3}{16}=0.1875\)

Step 5 ：\(\boxed{\text{a) The number that should replace A is 20.}}\)

Step 6 ：\(\boxed{\text{b) The probability of the total being 4 is }\frac{3}{16}\text{ or }0.1875\)