Defined numbers do not limit significant figures in an answer explain why

Concept:

Significant Figures: In the measured value of a physical quantity, the number of digits about the correctness of which we are sure plus the next doubtful digit, are called Significant Figures.

There are certain values of physical quantities which are defined; like irrational numbers ∛2, √3, the speed of light ( 299792458... m/s), converted value of centimeter in to inches (2.54...), refractive index of the glass with respect to the water ( 1.333) etc. These values are defined but they have no limit of significant figures because we can consider the measurement up to any extent which differ from the measurement to the measurement.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer