Let \( a, b, c>1 \), \( a^{3}, b^{3} \) and \( c^{3} \) be in A.P., and \( \log_{a} b, \log_{c} a \) and \( \log_{b} c \) be in G.P. If the sum of first \( 20 \) terms of an A.P., whose first term is \( \dfrac{a+4b+c}{3} \) and the common difference is \( \dfrac{a-8b+c}{10} \) is \( -444 \), then \( abc \) is equal to:
