The parameter 2/5 is a fraction while the parameter 0.4 is a decimal. You can convert the decimal into fraction by dividing the digit to its place value. Since 4 is in the tenths place,
0.4 = 4/10
Simplifying,
4/10 = 2/5
Thus, 2/5 = 0.4. When you multiply 100 to the decimal form, that would be expressed in percentage. Thus, 0.4 = 40%. The answer is B.