Suppose $| A | = | B | = | C | = 100 , | A \cap B | = 60 , | A \cap C | = 50 , | B \cap C | = 40 \text {, and } | A \cup B \cup C | = 175$

Suppose $| A | = | B | = | C | = 100 , | A \cap B | = 60 , | A \cap C | = 50 , | B \cap C | = 40 \text {, and } | A \cup B \cup C | = 175$ . How many elements are in $A \cap B \cap C$ ?