mass number is defined as sum of number of protons and neutrons
so here for Isotope A
Isotope A contains 56 protons and 80 neutrons.
Mass number will be given as

For Isotope B
Isotope B contains 55 protons and 81 neutrons.

For Isotope C
Isotope C contains 57 protons and 80 neutrons.

For Isotope D
Isotope D contains 56 protons and 74 neutrons.

<em>So here Isotope A and Isotope B has same mass number</em>
Explanation:
let's take the volume of each first:
ice cream: 10×10×4=400cm^3
freezer: 40×40×20=32,000cm^3
now we just divide: 32000/400=80
Answer:
The starting position is 3 m and the object is traveling at 3 m/s
Explanation:
distance(d) = speed(s) × time (t)
= 22.3 × 8.5
= 189.55m