The number of significant figures in the measurement of a length 0.079000 m is

The efficiency of an engine is given by $\eta=\frac{\alpha \beta}{\sin \theta} \cdot \log _e \frac{\beta x}{k T}$, where $\alpha$ and $\beta$ are constants. If $T$ is the absolute temperature, $k$ is Boltzmann constant, $\theta$ is angular displacement and $x$ is distance, then the incorrect statement is

Velocities $(v)$ and accelerations (a) in two systems of units 1 and 2 are related as $v_2=\frac{n}{m^2} v_1$ and $a_2=\frac{a_1}{m n}$ respectively. Here $m$ and $n$ are constants. Dimensionally relations between distances ( $s_1$ and $s_2$ ) and times ( $t_1$ and $t_2$ ) in the two systems are respectively

The number of significant figures in $3.78 \times 10^{22} \mathrm{~kg}$ is