ABCD is a quadrilateral in which AB|| DC, and E and F are the mid points of the diagonals AC and BD, respectively. If AB = 12 cm, BC = 40 cm, DC = 30 cm, and AD = 45 cm, then what is the length ( in cm) of EF?

ABCD is a quadrilateral in which AB|| DC, and E and F are the mid points of the diagonals AC and BD, respectively. If AB = 12 cm, BC = 40 cm, DC = 30 cm, and AD = 45 cm, then what is the length ( in cm) of EF?
ABCD एक चतुर्भुज है जिसमें AB ∥ DC है, तथा E और F क्रमशः विकर्णों AC और BD के मध्यबिंदु हैं। यदि AB = 12 सेमी, BC = 40 सेमी, DC = 30 सेमी और AD = 45 सेमी हैं, तो EF की लंबाई (सेमी में) ज्ञात कीजिए।