Are teacher is using this example but I dont understand how he got the numbers especially for the numbers beinf divided in the answer portion.

Barry Cuda is considering three different investments. He$,$ Iike most investors, is concerned about minimizing risk. Using the following information, which investment appears to have the least amount of risk relative to its expected return?

Investment A: expected return was calculated to be $18\%($$$19,000$;$17\%)$ with a standard deviation of $6\%($$$8000$;$8\%).$

Investment B: expected return was calculated to be $$15,000(14\%$;$15\%)$ with a standard deviation of $$6000(8\%$;$7\%).$

Investment C: expected return was calculated to be $20\%(20\%$;$$19,000)$ with a standard deviation of $8\%(8\%$;$$7000).$

$5$a$.$ Investment