in-browser calls (WebRTC)

What do we have now: 1. PHP website (psychology consultations) 2. Ability to allocate multiple VPS 2.1. For a website - Ubuntu Linux 2.2 For calls. 3. Website brings our clients to payment The task is to develop the following functionality of audio calls between browsers (WebRTC): 1. Two variants of "callers" (it is important that there is a possibility of making 50+ simultaneous calls) 1.1. Callers, who make outgoing calls only (clients) 1.2. Callers, who are in the queue (similar to the operator in the PBX) and receive incoming calls (employees). Have the ability to call back. 2. Simple outgoing call widget 2.1. This widget is activated only after payment. 2.2. Depending on the amount of prepayment, the conversation is limited in minutes. 2.3 Only after paying extra (preferably with one button in the widget), the call can be extended 3. Call parameters 3.1. Calls are successfully made between any modern browsers and platforms (smartphone, PC, Mac, etc.) 3.2. Standart statistics module This is not a one-time project, but only the first stage of development IMPORTANT: Please, write your best fixed offer of the cost and deadline for the task. (we can work with fixed payment or per hour, but fixed is preferred)