$2019_b$

$\begin{array} {lc} \text{Base 2 }\to \text{ base 8:} & \underbrace{011}_3 \underbrace{111}_7 \underbrace{100}_4 \underbrace{011}_3 \\ \text{Base 2 }\to \text{ base 16:} & \underbrace{0111}_7 \ \underbrace{1110}_E \ \underbrace{0011}_3 \\ \text{Base 16 }\to \text{ base 10:} & \overbrace{7 \times 16^2}^7 + \overbrace{14\times 16^1}^E + \overbrace{3\times 16^0}^3 & = 2019_{10} \end{array}$

Therefore $a\times b \times c \times d = 2 \times 0 \times 1 \times 9 = \boxed 0$ .

$\begin{aligned} 011111100011_2 &= 1024+512+256+128+64+32+2+1 = 2019_{10} \\ 3743_8 &= 3(512) + 7(64) + 4(8) + 3 = 2019_{10} \\ 7E3_{16} &= 7(256) + 14(16) + 3 = 2019_{10} \end{aligned}$

$2\times 0\times 1\times 9 = 0$

go to this webpage

https://www.tools4noobs.com/online tools/base convert/

and get the answer immediately.

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