Which of the following are exact number and which are measured numbers

Baby weighs 1.85 is measured number.

A baker's dozen is exact number.

5.0 microliters injection is measured.

79 students are exact numbers.

Explanation:

An exact number has no uncertainty in it. Measured numbers have a limited number of significant figure

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.