The junction diode in the following circuit requires a minimum current of 1mA to be above the knee point (0.7V) of its I-V characteristic curve. The voltage across the diode is independent of current above the knee point, If $V_B = 5V$, then the maximum value of R so that the voltage is above the knee point will be:

4.3k Ω

$V_B = V_{knee} + I_R$

or $5 = 0.7 + 10^{–3} R$ or $R = 4.3KΩ$