Beginning in the late 19th century and continuing into the

Question

Beginning in the late 19th century and continuing into the 20th century, the industrial revolution was fueled by coal and spewed enormous volumes of ¹⁴C-depleted CO₂ into the atmosphere. 

a) Why is coal ¹⁴C-depleted?

b) How would the increase in ¹⁴C-depleted CO₂ affect the date of a very old object in which its ¹⁴C/¹²C ratio was compared to the 20th-century ratio?